The presence of gas in the subdural space is not infrequently observed after and during lumbar pneumoencephalography.1 It has been proved at operation and at autopsy that the gas actually lies within the subdural space.2 The resultant subdural shadows have often been a source of confusion to the diagnostician, and are frequently interpreted as "gross cerebral atrophy." Recently, the presence of subdural shadows in encephalograms has been considered indicative, if not diagnostic, of subdural hematomas.3 Introduction of air into the subdural space has been recommended in the treatment of post-traumatic headache.4
There has been some difference of opinion concerning the mode of entry of gas into the intracranial subdural space after its presumptive introduction into the vertebral subarachnoid space. It is apparent that the mode of entry has a direct bearing on the diagnostic and therapeutic value of subdural gas.
It is the purpose of this
VON STORCH TJC, BUERMANN A. SUBDURAL SHADOWS IN PNEUMOENCEPHALOGRAMSTHEIR DIAGNOSIS, ORIGIN AND SIGNIFICANCE. Arch NeurPsych. 1939;42(5):810-825. doi:10.1001/archneurpsyc.1939.02270230032002